1. Field of the Invention
The present invention relates to a semiconductor device and a method for fabricating the same.
2. Description of the Related Art
A typical semiconductor device has a structure in which conductive patterns of a substrate are interconnected to pads of a semiconductor die attached to the upper surface of the substrate through wires.
The wires are made of gold or copper and the bond pads are made of aluminum. The use of the different metals gives rise to a potential difference between the wires and the bond pads. This potential difference allows electrons to migrate between the wires and the bond pads. As a result, the wires having a noble potential tend to corrode at a reduced rate and the bond pads having an active potential tend to corrode at an accelerated rate, resulting in corrosion at the interfaces between the wires and the bond pads. This corrosion is called “galvanic corrosion.”
Galvanic corrosion weakens the bonding between the conductive wires and the semiconductor die. That is, galvanic corrosion is considered to be a major factor that causes disconnection of the conductive wires from the semiconductor die, resulting in operational failure or malfunction of the semiconductor device.
In recent years, various attempts have been made to improve the performance of semiconductor devices. Particularly, methods have been proposed for stacking a plurality of semiconductor dies in one semiconductor device using film-over-wires (FOWs). According to these methods, however, galvanic corrosion between wires and bond pads becomes a more serious problem during heating for the solidification of the FOWs.